This blog is devoted to the application of optical fibers in photography. I have several homemade (DIY) flash adapters channeling the light from the flash close to the lens. The technique can be used mainly for macro photography, but I will show examples for wide angle close focus techniques as well. The recent version is called fiberstrobe V3, hence the name of the blog is "fiberstrobe".

Sunday, July 15, 2012

Twin-flash adapter step by step

The idea to create an adapter mimicking a twin flash came from the V3 design. This adapter included 4 flexible arms and it's attached to a bigger cobra-type external flash. Although the ring-flash adapter works well with my mirrorless camera (nex-5) I wanted something more versatile option. In addition, I always wanted to try a twin-flash but the price of the commercial products just distracted me. So I decided to create something similar. I had to find some solution for the support of the flexible arms, because it was obvious that a small flash of a mirrorless camera cannot hold it. So I designed a plate that will hold the arms and cut out it from fiberboard. Something more sturdy, such as aluminium plate would be even better. After drilling holes for the arm and the screw for the camera I painted it black:

This time I wanted to use ariana arms (see my previous post about flexible arms) but the local supplier I tried brought me loc-line. I used an Y-piece in the design but I had some difficulties to push through the fibers. You may try T-piece, and order all pieces in black version. The orange one looks a bit stupid:

It looks like that when fixed to the plate by screws (it was custom made and quite expensive):

After gluing the end of the fibers in the middle to a plastic piece (for details, check my previous post) and the next day I trimmed back and polished the ends. Depending on your flash powering the adapter, you may use some cardboard to attach the branch of fibers in the middle to your flash. I used a big plastic syringe (60 ml), because the head of my new flash is round shaped. I used for this final step hot glue to fix the blue plastic piece to the tube cut out from the syringe and aluminium folie to pad the tube inside and lots of duck tape to cover it outside (prevention of light leakage is very important). See the final form of the adapter below:

Alternatively, you may look around in the kitchen for some hard paper roll. The plastic material of the syringe was difficult to cut. You may attach any kind of light modifier to the end of your twin-flash adapter:

How it works? Like a twin flash:

In addition, it can create some very special light effect like this sea urchin lit from inside:

With this set-up:

The other advantage of this twin-flash adapter that it can be folded in many ways and it can be used even with wide angle or fisheye lenses:

No, it's not for triggering any other flash. It's to replace flash itself by splitting and channeling the light into new position. So the main light sources are the two ends of the arms.It's only for macro or close-ups. For this purpose any af the options you described would be more expensive, bulkier and you would probably lose TTL. And the wouldn't be as fexible as my twin adapter regarding positioning the light (for close range).

Great project! Could you tell me a little about the optical fiber you're using. I have to bring a little light over a distance of 8m into a very confined space. I'm interested in fiber dimension, transmission loss, and ideally where to buy. Cheers!

I just copy the same answer I gave in the dpreview discussion: Actually I lose a lot. Once I tried to calculate or estimate it but I gave up. One thing is the loss while the light is passing through the fiber (20% is lost through 1 meter pmma cable) but only a fraction of your flash surface area is covered by the optical fibers. Numerical aperture, the acceptance angle (30 degree) bending etc. also influence the light loss. However, whithout too much scientific calculations I can tell you that with my current optical fiber set ups used for macro photography I can use f16-f22 at base iso 200 without problem.

Sometimes I use the optical fibers without additional diffusers, but recently I like to add a flag (preventing light entering directly the lens in case of back lighting) and a stripe of diffusor paper around the end of my arms.